Implementing accelerated 3D is not yet finished. One of the reasons the foundation thought general users wouldn't yet be interested in the device. I'm afraid you'll have to wait a bit for the software to increase performance by leaps and bounds.

Similar things hold for the video playback. The CPU is a bit slow, and won't be able to decode anything bigger than about 320x200 (my rough estimate). However the GPU is a BEAST and will easily decode 1920x1080 HD video content. The thing is the GPU decodingis H264 only and has not yet been integrated in any video playing program that you might have tested.